Drive element and light deflection element

ABSTRACT

A drive element includes: a pair of drive parts placed so as to be aligned in one direction; a movable part placed between the pair of drive parts; a pair of support parts placed such that the pair of drive parts and the movable part are interposed therebetween; a pair of connection parts connecting the pair of support parts to the movable part; and a fixing part connected to at least each of the pair of drive parts in an alignment direction of the pair of drive parts. Both end portions of the pair of support parts are connected to the pair of drive parts, respectively, and gaps each having a predetermined length are provided between the pair of support parts and the pair of drive parts so as to extend in the alignment direction of the pair of drive parts.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/JP2022/003591 filed on Jan. 31, 2022, entitled “DRIVE ELEMENT ANDLIGHT DEFLECTION ELEMENT”, which claims priority under 35 U.S.C. Section119 of Japanese Patent Application No. 2021-025988 filed on Feb. 22,2021, entitled “DRIVE ELEMENT AND LIGHT DEFLECTION ELEMENT”. Thedisclosures of the above applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a drive element that rotates a movablepart about a rotation axis, and a light deflection element using thedrive element.

Description of Related Art

In recent years, by using micro electro mechanical system (MEMS)technology, drive elements that rotate a movable part have beendeveloped. In this type of drive element, a reflection surface islocated on the movable part, thereby allowing scanning to be performedat a predetermined deflection angle with light incident on thereflection surface. This type of drive element is installed in imagedisplay devices such as head-up displays and head-mounted displays. Inaddition, this type of drive element can also be used in laser radarsthat use laser beams to detect objects, etc.

“Shanshan Gu-Stoppel, Thorsten Giese, Hans-Joachim Quenzer, UlrichHofmann and Wolfgang Benecke, ‘PZT-Actuated and—Sensed ResonantMicromirrors with Large Scan Angles Applying Mechanical LeverageAmplification for Biaxial Scanning’, Micromachines, issued in 2017, Vol.8, Issue 7, P215” describes a drive element that rotates a mirror abouta rotation axis by driving a pair of support parts parallel to eachother. In the drive element, a drive part is placed at each of both endsof the pair of support parts. Both ends of the pair of support parts aredriven up and down by these drive parts. Accordingly, torsion isgenerated at a connection part connecting the middles of the pair ofsupport parts, so that a movable part located at the center of theconnection part rotates. Thus, a mirror placed on the movable partrotates about the rotation axis defined by the connection part.

The drive element configured as described above has a simpleconfiguration and thus can be easily formed. However, in the driveelement, the rotation angle of the movable part per 1 Vpp is small, sothat further improvement of the driving efficiency of the movable partis required.

SUMMARY OF THE INVENTION

A first aspect of the present invention is directed to a drive element.The drive element according to this aspect includes: a pair of driveparts placed so as to be aligned in one direction; a movable part placedbetween the pair of drive parts; a pair of support parts placed suchthat the pair of drive parts and the movable part are interposedtherebetween; a pair of connection parts connecting the pair of supportparts to the movable part; and a fixing part connected to at least eachof the pair of drive parts in an alignment direction of the pair ofdrive parts. Both end portions of the pair of support parts areconnected to the pair of drive parts, respectively. Gaps each having apredetermined length are provided between the pair of support parts andthe pair of drive parts so as to extend in the alignment direction ofthe pair of drive parts.

In the drive element according to this aspect, since the pair of supportparts and the pair of drive parts are separated from each other by thegaps, curving of support parts at the positions of the gaps is notinhibited by the drive parts. In addition, the driving force of eachdrive part generated around each gap is transmitted to the support partvia the connection range other than the gap. Therefore, the supportparts can be more efficiently driven by the drive parts, so that thedriving efficiency of the movable part can be increased.

A second aspect of the present invention is directed to a lightdeflection element. The light deflection element according to thisaspect includes the drive element according to the first aspect and areflection surface located on the movable part.

Since the light deflection element according to this aspect includes thedrive element according to the first aspect, the driving efficiency ofthe movable part can be increased. Therefore, the driving efficiency ofthe reflection surface can be increased, so that deflection of andscanning with light can be performed at a higher deflection angle.

The effects and the significance of the present invention will befurther clarified by the description of the embodiment below. However,the embodiment below is merely an example for implementing the presentinvention. The present invention is not limited to the description ofthe embodiment below in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a configuration of a drive elementaccording to an embodiment;

FIG. 2A is a plan view showing the configuration of the drive elementaccording to the embodiment;

FIG. 2B is a plan view showing a configuration of a drive elementaccording to a comparative example;

FIG. 3A shows a simulation result, obtained by simulation, of a drivingstate of each part when a movable part according to the embodiment is ata maximum deflection angle position;

FIG. 3B shows a simulation result, obtained by simulation, of a drivingstate of each part when a movable part according to the comparativeexample is at a maximum deflection angle position;

FIG. 4A is a graph showing a simulation result of examining thedisplacement of each of the positions of a support part and a drive partduring driving according to the embodiment;

FIG. 4B is a graph showing a simulation result of examining thedisplacement of each of the positions of a support part and a drive partduring driving according to the comparative example;

FIG. 5 is a plan view showing a configuration used for examining aninflection point of the support part according to the embodiment;

FIG. 6A is a graph showing a simulation result of a displacementdistribution of the support part in a vibration direction according tothe embodiment;

FIG. 6B is a graph showing the gradient of a waveform of thedisplacement distribution obtained by differentiating the graph in FIG.6A according to the embodiment; and

FIG. 7 shows a simulation result showing a relationship between thedepth of each slit and the driving efficiency of the movable partaccording to the embodiment.

It should be noted that the drawings are solely for description and donot limit the scope of the present invention by any degree.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present invention will be describedwith reference to the drawings. For convenience, in each drawing, X, Y,and Z axes that are orthogonal to each other are additionally shown. TheY-axis direction is a direction parallel to a rotation axis of a driveelement, and the Z-axis direction is a direction perpendicular to areflection surface located on a movable part.

FIG. 1 is a perspective view showing a configuration of a drive element1, and FIG. 2A is a plan view showing the configuration of the driveelement 1.

As shown in FIG. 1 and FIG. 2A, the drive element 1 includes a pair ofdrive parts 11, a pair of fixing parts 12, a pair of support parts 13, amovable part 14, and a pair of connection parts 15. A reflection surface20 is located on the upper surface of the movable part 14, whereby alight deflection element 2 is configured. The drive element 1 has asymmetrical shape in the X-axis direction and the Y-axis direction in aplan view.

The pair of drive parts 11 are placed so as to be aligned in the X-axisdirection. In a plan view, the shapes and the sizes of the pair of driveparts 11 are the same as each other. The shape of each drive part 11 isa rectangular shape in a plan view in the case where no slit S1 isformed therein. The pair of drive parts 11 are placed such that ends onthe inner side (movable part 14 side) thereof are parallel to the Yaxis.

The pair of fixing parts 12 are placed such that the pair of drive parts11 are interposed therebetween in the X-axis direction. The pair offixing parts 12 have a constant width in the X-axis direction and extendparallel to the Y-axis direction. The drive element 1 is installed on aninstallation surface by installing the fixing parts 12 on theinstallation surface. The inner boundaries of the pair of fixing parts12 are connected to the outer boundaries of the pair of drive parts 11and the pair of support parts 13.

The pair of support parts 13 are placed such that the pair of driveparts 11 and the movable part 14 are interposed therebetween in theY-axis direction. The pair of support parts 13 have a constant width inthe Y-axis direction and extend parallel to the X-axis direction. Theouter boundaries of the pair of support parts 13 are connected to theinner boundaries of the pair of fixing parts 12. In addition, endportions on both sides in the X-axis direction of the pair of supportparts 13 are connected to the boundaries in the Y-axis direction of thepair of drive parts 11.

The movable part 14 is placed between the pair of drive parts 11. In theY-axis direction, the center position of the movable part 14 coincideswith the middle positions of the pair of drive parts 11. In the X-axisdirection, the center position of the movable part 14 coincides with themiddle positions of the pair of support parts 13. Here, the shape of themovable part 14 is a circular shape in a plan view. The shape of themovable part 14 in a plan view may be a shape other than a circularshape, such as a square shape. The reflection surface is located on theupper surface of the movable part 14. The reflection surface 20 islocated on the upper surface of the movable part 14, for example, byforming a reflection film thereon by vapor deposition or the like. Thereflection surface may be formed by subjecting the upper surface of themovable part 14 to mirror finish.

The pair of connection parts 15 connect the pair of support parts 13 tothe movable part 14. The pair of connection parts 15 extend in astraight manner from the middle positions in the X-axis direction of thepair of support parts 13 toward the movable part 14 and are connected tothe middle position in the X-axis direction of the movable part 14. Thewidths in the X-axis direction of the pair of connection parts 15 areconstant. The lengths in the Y-axis direction of the pair of connectionparts 15 are equal to each other. A cross-sectional shape of eachconnection part 15 when the connection part 15 is cut along a planeparallel to the X-Z plane is a rectangular shape whose upper side isparallel to the X-Y plane.

A slit S1 is formed at each of both ends in the Y-axis direction of thepair of drive parts 11. The slits S1 are formed so as to extend outwardfrom the ends on the inner side (movable part 14 side) of the pair ofdrive parts 11 by a predetermined length (depth). The slits S1 areformed by cutting the pair of drive parts 11 in a straight line from theends on the inner side of the drive parts 11 toward the outer side. Thewidths and the lengths (depths) of the four slits S1 are equal to eachother. Gaps are formed between the drive parts 11 and the support parts13 by the four slits S1. The drive parts 11 and the support parts 13 areseparated from each other by the gaps.

Piezoelectric drivers 11 a are placed on the upper surfaces of the pairof drive parts 11. That is, the pair of drive parts 11 each include thepiezoelectric driver 11 a as a drive source. In a plan view, eachpiezoelectric driver 11 a has a rectangular shape. The width of thepiezoelectric driver 11 a in the Y-axis direction is equal to the widthin the Y-axis direction of a portion, of the drive part 11, interposedbetween the two slits S1. In addition, the outer boundary of thepiezoelectric driver 11 a coincides with the inner boundary of thefixing part 12.

The piezoelectric driver 11 a has a lamination structure in whichelectrode layers are placed on the upper and lower sides of apiezoelectric thin film having a predetermined thickness, respectively.The piezoelectric thin film is made of, for example, a piezoelectricmaterial having a high piezoelectric constant, such as lead zirconatetitanate (PZT). The electrode layers are made of a material having lowelectrical resistance and high heat resistance, such as platinum (Pt).The piezoelectric driver 11 a is placed by forming the laminationstructure, which includes the piezoelectric thin film and the electrodelayers on the upper and lower sides thereof, on the upper surface of asubstrate included in the region of the piezoelectric driver 11 a by asputtering method or the like.

A substrate of the drive element 1 has the same contour as the driveelement 1 in a plan view, and has a constant thickness. The reflectionsurface 20 and the piezoelectric drivers 11 a are placed incorresponding regions of the upper surface of the substrate. Thethicknesses of the fixing parts 12 are increased by further stacking apredetermined material on the lower surfaces of portions, of thesubstrate, corresponding to the fixing parts 12. The material stacked atthe fixing parts 12 may be a material different from that of thesubstrate, or may be the same material as that of the substrate.

The substrate is, for example, integrally formed from silicon or thelike. However, the material forming the substrate is not limited tosilicon, and may be another material. The material forming the substrateis preferably a material having high mechanical strength and Young'smodulus, such as metal, crystal, glass, and resin. As such a material,in addition to silicon, titanium, stainless steel, Elinvar, a brassalloy, etc., can be used. The same applies to the material stacked onthe substrate at each fixing part 12.

The pair of drive parts 11 are curved in the Z-axis direction when adrive signal is supplied from a drive circuit which is not shown to thepiezoelectric drivers 11 a. Accordingly, the pair of support parts 13are curved in the Z-axis direction. As a result, the connection parts 15are twisted around a rotation axis R0, and the movable part 14 rotatesabout the rotation axis R0. Accordingly, the reflection surface 20rotates about the rotation axis R0.

The reflection surface 20 reflects light incident thereon from above themovable part 14, in a direction corresponding to a deflection angle ofthe movable part 14. Accordingly, the light (e.g., laser beam) incidenton the reflection surface 20 is deflected and scanning is performed withthis light as the movable part 14 rotates.

In the present embodiment, as described above, the slits S1 each havinga predetermined length (depth) are formed near the boundaries betweenthe pair of drive parts 11 and the pair of support parts 13, and thepair of drive parts 11 and the pair of support parts 13 are separatedfrom each other at the positions of these slits S1. Accordingly, thedriving efficiency of the movable part 14 and the reflection surface 20can be made higher than that in the case where these slits S1 are notformed.

FIG. 2B is a plan view showing a configuration example (comparativeexample) of the drive element 1 in the case where no slit S1 is formed.In the comparative example, the inner boundary of each drive part 11extends to the inner boundaries of the pair of support parts 13 and isconnected to the support parts 13.

The inventor confirmed that in the configuration of the comparativeexample in FIG. 2B, the rotation angle of the movable part 14 per 1 Vppis small, and thus the reflection surface 20 cannot be rotatedefficiently during light scanning. As a result of an intensive study,the inventor newly found that the driving efficiency of the movable part14 can be increased by adding a simple configuration of forming theslits S1 (gaps) near the boundaries between the pair of drive parts 11and the pair of support parts 13 as shown in FIG. 1 and FIG. 2A.

FIG. 3A shows a simulation result, obtained by simulation, of a drivingstate of each part when the movable part according to the embodiment isat a maximum deflection angle position. FIG. 3B shows a simulationresult, obtained by simulation, of a driving state of each part when themovable part according to the comparative example is at a maximumdeflection angle position.

As shown in FIGS. 3A and 3B, in each of the configurations of theembodiment and the comparative example, the pair of drive parts 11 aredriven in directions opposite to each other, whereby the pair of supportparts 13 are curved in opposite directions with the connection positionsof the pair of connection parts 15 as boundaries. Accordingly, the pairof connection parts 15 are twisted around the rotation axis R0. Due tothis twisting, the movable part 14 rotates about the rotation axis R0.As can be seen by comparing FIGS. 4A and 4B, in the configuration of theembodiment, by providing the slits S1, the drive parts 11 vibrate moregreatly than in the comparative example. Arrows in FIGS. 3A and 3Bindicate the displacement direction of each part.

FIG. 4A is a graph showing a simulation result of examining thedisplacement of each of the positions of the support part 13 and thedrive part 11 during driving according to the embodiment. FIG. 4B is agraph showing a simulation result of examining the displacement of eachof the positions of the support part 13 and the drive part 11 duringdriving according to the comparative example. FIGS. 4A and 4B show thewaveforms of the support part 13 and the drive part 11 when the supportpart 13 vibrates to the highest degree.

In FIGS. 4A and 4B, the horizontal axis shows the position in the X-axisdirection (separation distance from the rotation axis R0) in the casewhere the position of the rotation axis R0 is defined as 0. Here, aposition in the X-axis positive direction is indicated by a positivevalue, and a position in the X-axis negative direction is indicated by anegative value. The vertical axis shows the amount of displacement inthe Z-axis direction in the case where the positions of the drive part11 and the support part 13 when not curved (in a horizontal state) aredefined as 0. The amount of displacement of the drive part 11 is theamount of displacement of each position in the X-axis direction at themiddle position in the Y-axis direction of the drive part 11, and theamount of displacement of the support part 13 is the amount ofdisplacement of each position in the X-axis direction at the middleposition in the Y-axis direction of the support part 13.

In the examination in FIGS. 4A and 4B, the overall length in the X-axisdirection of the support part 13 was set to 7789 μm, and the overalllength in the X-axis direction of the drive part 11 was set to 1865 μm.In addition, the depth in the X-axis direction of each slit S1 was setto 846 μm. The deepest position in the X-axis direction of each slit S1corresponds to the position in the X-axis direction of an inflectionpoint of the support part 13 described later.

First, referring to FIG. 4B, in the comparative example, the gradient ofthe waveform showing the displacement of the support part 13 switchesbetween increasing and decreasing with positions P1 and P2 asboundaries. That is, on the left side of the position P1, the waveformof the support part 13 has a shape that is convex upward, and on theright side of the position P1, the waveform of the support part 13 has ashape that is convex downward. On the left side of the position P2, thewaveform of the support part 13 has a shape that is convex upward, andon the right side of the position P2, the waveform of the support part13 has a shape that is convex downward. Meanwhile, in the comparativeexample, the gradient of the waveform showing the displacement of thedrive part 11 is either increasing or decreasing. That is, the waveformof the drive part 11 on the left side has a shape that is convex upwardover the entire range, and the waveform of the drive part 11 on theright side has a shape that is convex downward over the entire range.

Therefore, in the comparative example, in ranges W1 and W2 in FIG. 4B,the curving directions of the drive part 11 and the support part 13 areopposite to each other. That is, in the range W1, the drive part 11 iscurved convexly upward, but the support part 13 is curved convexlydownward. In the range W2, the drive part 11 is curved convexlydownward, but the support part 13 is curved convexly upward. As shown inFIG. 2B, in the comparative example, in the ranges W1 and W2, theboundaries of each drive part 11 and each support part 13 are connectedto each other. Therefore, in the ranges W1 and W2, the curving of thesupport part 13 is inhibited by the opposite curving on the drive part11 side. As a result, in the comparative example, the support part 13 isnot efficiently driven by the driving force of the drive part 11, sothat the driving efficiency of the movable part 14 is decreased.

On the other hand, in the configuration of the embodiment, as shown inFIG. 2A, the slits S1 are formed in the ranges W1 and W2, whereby eachdrive part 11 and each support part 13 are separated from each other.Therefore, in the configuration of the embodiment, in the ranges W1 andW2, the curving of the support part 13 is not inhibited by the oppositecurving on the drive part 11 side. Accordingly, in the embodiment, asshown in FIG. 4A, the waveform of the support part 13 and the waveformof the drive part 11 are widely separated from each other. In addition,the driving force generated in the portion of the drive part 11interposed between the two slits S1 is transmitted from the drive part11 to the support part 13 via the connection position other than theslits S1. Therefore, in the configuration of the embodiment, the supportpart 13 can be more efficiently driven by the driving force of the drivepart 11, so that the driving efficiency of the movable part 14 can beincreased.

Next, the inventor examined the relationship between the depth of eachslit S1 in the X-axis direction and the driving efficiency of themovable part 14 by simulation.

First, the inventor obtained an inflection point at which the gradientof the support part 13 which is curved when the movable part 14 isdriven switches between increasing and decreasing, by simulation. Here,as shown in FIG. 5 , the above inflection point was obtained for thesupport part 13 having a constant width in the Y-axis direction and alength of L1. The length L1 was set to 7789 μm as in the examination inFIGS. 4A and 4B. Under these conditions, the distribution ofdisplacement in the Z-axis direction in a vibration mode that generatesa gradient in a center portion of the support part 13 (secondaryvibration mode when both ends are fixed) was analyzed.

FIG. 6A is a graph showing a simulation result of the displacementdistribution of the support part 13 in the vibration direction (Z-axisdirection). FIG. 6B is a graph showing the gradient of a waveform of thedisplacement distribution obtained by differentiating the graph in FIG.6A.

In FIGS. 6A and 6B, the horizontal axis shows the position in the X-axisdirection (separation distance from the rotation axis R0) in the casewhere the middle position of the support part 13 in the X-axis directionis defined as 0. Here, a position in the X-axis positive direction isindicated by a positive value, and a position in the X-axis negativedirection is indicated by a negative value. In FIG. 6A, the verticalaxis shows the amount of displacement in the Z-axis direction in thecase where the position of the support part 13 when not curved (in ahorizontal state) is defined as 0, and in FIG. 6B, the vertical axisshows the gradient of the waveform in FIG. 6A. In each of FIGS. 6A and6B, the vertical axis is normalized by a predetermined value.

In FIGS. 6A and 6B, the positions of dashed circles are inflectionpoints. At each of these positions, the gradient of the amplitudewaveform of the support part 13 switches between increasing anddecreasing. In this simulation result, a distance D1 from each end ofthe support part 13 to each inflection point P0 was 1019 μm. Asdescribed above, in the examination in FIG. 4A, the deepest position ofeach slit S1 is set at the position of the inflection point P0 in theX-axis direction.

After obtaining the inflection points P0 as described above, theinventor obtained the relationship between the depth of each slit S1 inthe X-axis direction and the driving efficiency of the movable part 14by simulation.

FIG. 7 shows a simulation result showing the relationship between thedepth of each slit S1 and the driving efficiency of the movable part 14.

In FIG. 7 , on the horizontal axis, the depth of the slit S1 is definedwith the depth of the slit S1 as 0 in the case where the slit S1 extendsto the inflection point P0 obtained in FIGS. 6A and 6B. A positive valueon the horizontal axis indicates a value at which the depth of the slitS1 decreases, and a negative value on the horizontal axis indicates avalue at which the depth of the slit S1 increases. In FIG. 7 , on thevertical axis, the total of the deflection angle of the movable part 14(reflection surface 20) per 1 Vpp is indicated by a value normalized bythe maximum value of the simulation result.

In this simulation, in the configuration in FIG. 2A, the length in theX-axis direction of each support part 13 was set to 7789 μm, and thewidth in the X-axis direction of each drive part 11 in the region otherthan the slits S1 was set to 1865 μm. Under these conditions, the depth(length in the X-axis direction) of each slit S1 was changed, and thedriving efficiency of the movable part 14 and the reflection surface 20was obtained.

Here, the depth of the slit S1 (the value on the horizontal axis in FIG.7 ) was changed to six types: −510 μm, −369 μm, −255 μm, 0 μm, 423 μm,and 846 μm. The plot at 846 μm on the horizontal axis corresponds to thecase where the depth of the slit S1 is 0, that is, no slit S1 is formedas in the comparative example in FIG. 2B. The depth of the slit S1 inthe case where the value on the horizontal axis is 0, that is, in thecase where the slit S1 extends to the inflection point P0, is 846 μm.

As shown in FIG. 7 , the driving efficiency of the movable part 14gradually increased as the slit S1 became deeper. When the deepestposition of the slit S1 corresponded to the position of the inflectionpoint P0, the driving efficiency of the movable part 14 became thehighest, and then the driving efficiency of the movable part 14decreased as the slit S1 became deeper. When the depth of the slit S1 isexcessively large as in the leftmost plot in FIG. 7 , the drivingefficiency of the movable part 14 became lower than that in the casewhere no slit S1 was provided (rightmost plot). Accordingly, it isconfirmed that the depth of the slit S1 has a range suitable forimproving the driving efficiency.

That is, in the examinaiton result in FIG. 7 , it is confirmed that atleast in the range to the depth corresponding to the second plot fromthe left, the driving efficiency of the movable part 14 becomes higherthan that in the case where there is no slit S1. The depth (length inthe X-axis direction) of the slit S1 corresponding to the second plotfrom the left is a depth extended by 369 μm from 864 μm, which is thedepth of the slit S1 in the case where the slit S1 is extended to theinflection point P0. Therefore, from this examinaiton result, it isfound that by setting the depth of the slit S1 in a range further to thedepth larger by 44% (369 μm/846 μm) than the depth to the inflectionpoint P0, the driving efficiency of the movable part 14 can be madehigher than that in the case where there is no slit S1. In addition,from the examinaiton result in FIG. 7 , it is also found that withinthis range, the depth to the inflection point P0 can increase thedriving efficiency of the movable part 14 the most.

Therefore, from this examinaiton result, the depth of the slit S1 in theX-axis direction is preferably set within a range having, as an upperlimit, a depth larger by about 40% than the depth to the inflectionpoint P0, and is more preferably set to around the depth to theinflection point P0. Accordingly, the driving efficiency of the movablepart 14 can be increased, and deflection of and scanning with light canbe performed at a higher deflection angle by the reflection surface 20.

Effects of Embodiment

According to the embodiment, the following effects can be achieved.

As shown in FIG. 1 and FIG. 2A, the pair of support parts 13 and thepair of drive parts 11 are separated from each other by the gaps (slitsS1), and thus the curving of the support parts 13 at the positions ofthe gaps (slits S1) is not inhibited by the drive parts 11. In addition,the driving force of each drive part 11 generated around each gap (slitS1) is transmitted to the support part 13 via the connection range otherthan the gap (slit S1). Therefore, as shown in the examination result inFIG. 7 , the support parts 13 can be more efficiently driven by thedrive parts 11, so that the driving efficiency of the movable part 14can be increased. As a result, the driving efficiency of the reflectionsurface 20 can be increased, so that deflection of and scanning withlight can be performed at a higher deflection angle.

As shown in FIG. 1 and FIG. 2A, the gaps are formed between the pair ofsupport parts 13 and the pair of drive parts 11 by forming the slits S1in the alignment direction of the pair of drive parts 11 (X-axisdirection) from the ends on the movable part 14 side of the pair ofdrive parts 11. Accordingly, the gaps can be formed continuously fromthe ends on the movable part 14 side of the pair of drive parts 11, sothat the driving efficiency of the movable part 14 can be smoothlyincreased.

The depth of each slit S1 in the alignment direction of the pair ofdrive parts 11 (X-axis direction) is preferably set within a rangehaving, as an upper limit, a depth larger by about 40% than the depth tothe inflection point P0 at which the gradient of the waveform (gradientof the displacement in the thickness direction) of the support part 13which is curved when the movable part 14 is driven switches betweenincreasing and decreasing. Accordingly, as shown in the examinationresult in FIG. 7 , the driving efficiency of the movable part 14 can beeffectively made higher than that in the case where there is no gap(slit S1).

The depth of each slit S1 in the alignment direction of the pair ofdrive parts 11 (X-axis direction) is further preferably set to aroundthe depth to the inflection point. Accordingly, as shown in theexamination result in FIG. 7 , the driving efficiency of the movablepart 14 can be further effectively increased.

As shown in FIG. 1 and FIG. 2A, each drive part 11 includes thepiezoelectric driver 11 a as a drive source. Accordingly, the movablepart 14 can be driven with high driving efficiency.

<Modifications>

In the above embodiment, the gap is formed between each drive part 11and each support part 13 by continuously forming the slit S1 having aconstant width in the Y-axis direction, but the method for forming thegap is not limited thereto. For example, the width in the Y-axisdirection of the gap may be changed depending on the position in theX-axis direction by changing the width of the drive part 11 or thesupport part 13 in the X-axis direction. The gap does not have to becontinuous in the X-axis direction, and may be formed intermittently inthe X-axis direction. However, in order to further increase the drivingefficiency of the movable part 14, it is preferable that the gap isformed continuously in the X-axis direction from the end on the movablepart 14 side of the drive part 11 as in the above embodiment.

The shape of the drive element 1 in a plan view and the dimensions ofeach part of the drive element 1 are also not limited to those shown inthe above embodiment, and can be changed as appropriate. The shape andthe size of each piezoelectric driver 11 a in a plan view can also bechanged as appropriate. In addition, the thickness, the length, thewidth, and the shape of each fixing part 12 can also be changed asappropriate. For example, the thickness of each fixing part 12 may beequal to the thicknesses of each drive part 11 and each support part 13.The thickness, the width, and the shape of each fixing part 12 can bechanged as appropriate as long as the drive element 1 can be installedon the installation surface.

In the above embodiment, both ends of the pair of support parts 13 areconnected to the pair of fixing parts 12, but both ends of the supportparts 13 do not have to be connected to the fixing parts 12. Forexample, the width in the Y-axis direction of each fixing part 12 may beset to be equal to the width in the Y-axis direction of each drive part11, and both end portions of the support parts 13 may be connected toonly both edges in the Y-axis direction of the drive parts 11. In thiscase as well, the driving efficiency of the movable part 14 can beincreased by providing gaps (slits S1) between the support parts 13 andthe drive parts 11. In addition, in the configuration in FIG. 1 , bothends in the Y-axis direction of fixing parts 12 may be further connectedin the X-axis direction to form a fixing part. That is, a fixing part 12may be formed so as to surround the pair of drive parts 11 and the pairof support parts 13 in a plan view.

The drive element 1 may be used as an element other than the lightdeflection element 2. In the case where the drive element 1 is used asan element other than the light deflection element 2, the reflectionsurface 20 does not have to be placed on the movable part 14, and amember other than the reflection surface 20 may be placed thereon.

In addition to the above, various modifications can be made asappropriate to the embodiment of the present invention, withoutdeparting from the scope of the technological idea defined by theclaims.

What is claimed is:
 1. A drive element comprising: a pair of drive partsplaced so as to be aligned in one direction; a movable part placedbetween the pair of drive parts; a pair of support parts placed suchthat the pair of drive parts and the movable part are interposedtherebetween; a pair of connection parts connecting the pair of supportparts to the movable part; and a fixing part connected to at least eachof the pair of drive parts in an alignment direction of the pair ofdrive parts, wherein both end portions of the pair of support parts areconnected to the pair of drive parts, respectively, and gaps each havinga predetermined length are provided between the pair of support partsand the pair of drive parts so as to extend in the alignment directionof the pair of drive parts.
 2. The drive element according to claim 1,wherein the gaps are provided by forming slits in the alignmentdirection of the pair of drive parts from ends on the movable part sideof the pair of drive parts.
 3. The drive element according to claim 2,wherein a depth of each of the slits in the alignment direction of thepair of drive parts is set within a range having, as an upper limit, adepth larger by about 40% than a depth to an inflection point at which agradient of displacement in a thickness direction of the support partwhich is curved when the movable part is driven switches betweenincreasing and decreasing.
 4. The drive element according to claim 3,wherein the depth of each of the slits is set to around the depth to theinflection point.
 5. The drive element according to claim 1, whereineach of the drive parts includes a piezoelectric driver as a drivesource.
 6. A light deflection element comprising: a drive elementincluding a pair of drive parts placed so as to be aligned in onedirection, a movable part placed between the pair of drive parts, a pairof support parts placed such that the pair of drive parts and themovable part are interposed therebetween, a pair of connection partsconnecting the pair of support parts to the movable part, and a fixingpart connected to at least each of the pair of drive parts in analignment direction of the pair of drive parts, and a reflection surfacelocated on the movable part, wherein both end portions of the pair ofsupport parts are connected to the pair of drive parts, respectively,and gaps each having a predetermined length are provided between thepair of support parts and the pair of drive parts so as to extend in thealignment direction of the pair of drive parts.
 7. The light deflectionelement according to claim 6, wherein the gaps are provided by formingslits in the alignment direction of the pair of drive parts from ends onthe movable part side of the pair of drive parts.
 8. The lightdeflection element according to claim 7, wherein a depth of each of theslits in the alignment direction of the pair of drive parts is setwithin a range having, as an upper limit, a depth larger by about 40%than a depth to an inflection point at which a gradient of displacementin a thickness direction of the support part which is curved when themovable part is driven switches between increasing and decreasing. 9.The light deflection element according to claim 8, wherein the depth ofeach of the slits is set to around the depth to the inflection point.10. The light deflection element according to claim 6, wherein each ofthe drive parts includes a piezoelectric driver as a drive source.